(backport of 6b9f547e92d8)

Remove a sleep to fix transient test failures. Use skewfactor of -3 to
make it work on systems that have 1 second precision for time.time().

Closes #11999
Refs #13254

when called with a timeout.  Patch by Arnaud Ysmal.

Issue #13237: Fix formatting error - the legacy shell commands weren't meant to be under the Notes heading

Issue #13237: Forward port subprocess module updates and explicitly document UTF-8 encoding assumption when universal_newlines=True

Issue #13340.

Issue #10570

error handler in interactive mode (when calling into PyOS_Readline()).

Closes #13340.

The find utility of OpenBSD doesn't support the "-exec cmd {} +"
action. Change it to use "-depth -exec cmd {} ;" instead.

Also, remove __pycache__ before *.py[co], as most bytecode files are
in __pycache__ directories. Only those generated by Python 2 under
Doc/tools are not.

Closes #13326.